1. The invention is directed to a safety device in web-fed rotary printing machines at cylinders with a feed gap and, more particularly, to cylinders of a printing mechanism which are in a drive connection via gear wheels.
2. Description of the Prior Art
Problems may occur in web-fed rotary printing machines when foreign bodies enter the feed gap between two adjacent cylinders. This occurs, for example, due to wound up paper, breakage of plates and tearing of rubber blankets. It is known from general background art to provide predetermined breaking points in the couplings of the longitudinal shaft in web-fed rotary printing machines which separate the printing unit from the main shaft in the event of an accident in the printing unit. However, it may often be observed in the cases of disruption mentioned above that damage nevertheless occurs within the drive of the printing unit. For example, the drive wheels clamped on the cylinder pins will :bond with the cylinder pins. Repair in this case is costly and requires that the entire cylinder be replaced.
To prevent such damage it would also be possible to bring the cylinder pin into a friction-locking drive connection with the cylinder gear via a friction clutch or a slip clutch. However, it is difficult to accommodate such safety clutches on the cylinder pins due to their length, since spatial conditions are cramped due to other mechanisms such as those for adjusting the register. Moreover, such clutches require that the cylinder gear be mounted on the cylinder pin via roller bearings. This leads to all unacceptable increase in the radial deviation or true-running discrepancy of the cylinder gear. Further, the roller bearings are mainly statically loaded in an unfavorable manner.